SV: Re: SV: Re: [sdiy] Compensating PTC and NTC resistors

Amos controlvoltage at
Wed Mar 19 17:50:25 CET 2008

>> Any non-trivial circuit will be difficult to understand the *complete*
>> picture. That's why we make approximations.  The resistor is just
>> one such approximation.  It gets us "close enough" to perfection at minimal
>> cost.
>Approximations are not always a neat solution to a problem.
>Making approximations on saftey critically systems are dangerous
>engineering behavior.Close enough are no cigar.

There is nothing wrong with either of these statements, but I question
their relation to each other.  Specifically, if you are designing
critical safety systems whose success/failure depends upon knowing the
exact TC of the carbon resistors, maybe your design isn't safe enough.
 In that case, I assume that an approximation would be used to
estimate the "absolute worst possible case" of temperature drift, to
be sure that your design could not be negatively affected by this

I apologise for not contributing usefully to this discussion.


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